The present invention relates to mechanical seals of the type used for sealing a rotating shaft in a stuffing box.
Fluid seals for rotating shafts or the like may be of various types. In one type the sealing joint is formed by the rubbing juncture of two rigid materials, e.g., metal to metal or ceramics to graphite. In this case, the sealing surfaces must be machined, ground and lapped to very precise tolerances in order to obtain a fluid tight joint. Consequently, in manufacturing such seals to exacting requirements considerable labor is involved, and the seals are therefore very expensive and often impractical.
Another type of seal effects sealing by the rubbing contact of a flexible material, such as rubber, leather or the like, directly with a moving shaft or stuffing box surface. Although such seals are suitable for use under less exacting conditions, and are less expensive to manufacture than the aforementioned machined seals, as a result of friction when the flexible sealing material is rubbed against a dry surface the material may be subjected to heating, excessive wear, and loss of its sealing effect. Thus, in use the material must either be saturated with lubricant or lubricant otherwise supplied thereto, for example by seepage of the sealed off liquid.